CVE-2015-6975 in Mac OS X
Summary
by MITRE
CoreText in Apple iOS before 9.1, OS X before 10.11.1, and iTunes before 12.3.1 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted font file, a different vulnerability than CVE-2015-6992 and CVE-2015-7017.
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Analysis
by VulDB Data Team • 06/24/2022
The vulnerability identified as CVE-2015-6975 represents a critical memory corruption flaw within Apple's CoreText framework affecting multiple operating systems including iOS versions prior to 9.1, macOS versions before 10.11.1, and iTunes versions before 12.3.1. This vulnerability resides in the font processing capabilities of the CoreText subsystem which is responsible for text rendering and font handling across Apple's ecosystem. The flaw manifests when the system processes specially crafted font files that contain malformed data structures, leading to unpredictable behavior in the memory management of affected applications.
The technical nature of this vulnerability involves improper input validation and memory handling within CoreText's font parsing routines. When a malicious font file is processed, the framework fails to properly validate the font's structure and memory allocation patterns, resulting in memory corruption that can be exploited to execute arbitrary code or cause system crashes. This type of vulnerability falls under the CWE-125 vulnerability class, which describes out-of-bounds read conditions where an application reads memory beyond the intended buffer boundaries. The exploitation mechanism leverages the font rendering pipeline to manipulate memory layout and potentially overwrite critical system structures or execute malicious code within the context of the affected application.
From an operational perspective, this vulnerability presents significant risk to Apple device users as it can be remotely exploited through malicious font files delivered via email attachments, web pages, or file sharing platforms. The impact extends beyond simple denial of service to potentially full system compromise, as successful exploitation allows attackers to execute arbitrary code with the privileges of the affected application. This vulnerability is particularly dangerous because CoreText is deeply integrated into Apple's operating systems and is used by numerous applications including web browsers, email clients, and document viewers, making the attack surface quite broad. The vulnerability's classification aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation often involves code execution through legitimate system interfaces.
The exploitation of CVE-2015-6975 requires minimal user interaction, typically only requiring the opening of a malicious font file or visiting a web page containing such content. Attackers can leverage this vulnerability in phishing campaigns, social engineering attacks, or by compromising websites that serve malicious fonts. The memory corruption occurs during font processing, which means that any application utilizing CoreText for font rendering becomes a potential target for exploitation. The vulnerability demonstrates the importance of input validation in system libraries and highlights how seemingly benign components like font rendering can become attack vectors when proper security measures are not implemented. Security professionals should note that this vulnerability represents a classic example of how improper memory handling in system libraries can lead to severe security implications across an entire operating system ecosystem.